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Wavefront Technology in Eye
Exams
Wavefront technology
revolutionizes eye
examinations to the extent
that, some day, familiar eye
charts and instruments
traditionally used for
diagnosis of vision errors
may become obsolete.
Most of us have undergone
eye examinations with a
device known as a phoropter,
fitted with various lenses
of different powers. An
ophthalmologist or
optometrist changes out the
lenses and quizzes us about
which lens produces the best
image.
But with this conventional
approach, information we
give the eye care
practitioner can be very
subjective, based more on
what we think we see instead
of what we actually see. A
wavefront analysis instead
is objective, because vision
errors can be automatically
identified by the way light
waves travel through the
eye.
Wavefront eye analysis also
potentially could replace
conventional eyeglass or
contact lens prescriptions,
which describe visual
problems in terms of the
eye's roundness (sphere),
irregular curvature
(cylinder), and orientation
needed for the corrective
artificial lenses (axis).
This information helps
identify the type and
severity of vision errors we
may have. But compared with
conventional methods,
wavefront analysis can
provide much more detail
about vision errors.
Wavefront analysis also has
been incorporated into
vision correction surgeries
such as LASIK.
Wavefront eye exams
automatically and
objectively measure vision
errors within a few minutes
and in much greater detail
than conventional methods.
What Is a Wavefront?
In the simplest terminology,
a wavefront can be explained
by picturing light traveling
as a bundle of rays. If you
draw lines perpendicular to
the tips of a bundle of
light rays, you obtain what
is called a wavefront map.
In an eye with perfect
vision, the wavefront is
perfectly flat. The
wavefront of an imperfect
eye is irregular.
Types of distortions this
wavefront acquires as it
travels through the eye
provide valuable information
about vision errors and how
to correct them.
Wavefront Technology
(Aberrometry):
Aberrometry measures the way
a wavefront of light passes
through various refractive
or focusing components of
the eye, such as the eye's
clear front surface (cornea)
and crystalline lens.
Different distortions that
occur as light travels
through the eye are known as
monochromatic aberrations,
representing specific vision
errors.
Wavefront technology, or
aberrometry, diagnoses both
lower- and higher-order
vision errors represented by
the way the eye refracts or
focuses light. Higher-order
aberrations are more complex
vision errors, whereas
lower-order aberrations are
more common vision errors
such as nearsightedness,
farsightedness, and
astigmatism.
Wavefront and Higher-Order
Aberrations
Previously, with
conventional methods of eye
examinations, only
lower-order vision errors
could be diagnosed and
treated. Higher-order
aberrations such as coma,
trefoil, and spherical
aberration were largely
ignored by eye care
professionals because their
impact on vision was
believed at the time to be
slight and because no
feasible means existed to
precisely identify or
correct them.
Now that higher-order
aberrations can be
accurately defined by
wavefront technology and
corrected by new kinds of
spectacles, contact lenses,
intraocular lenses, and
refractive surgery (adaptive
optics), they have become
more important factors in
eye examinations.
In the past, these
higher-order aberrations
received even more attention
because they were identified
as sometimes serious side
effects of refractive
surgery, showing up as
halos, ghosts, and a host of
other debilitating vision
symptoms. Newer
wavefront-guided lasers used
in vision correction
surgery, however, now have
been shown to have the
ability to reduce certain
higher-order aberrations,
which potentially can
improve low light image
quality during activities
such as driving at night.
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